Heleyna was a Time Lord engineer who was able to contact the War Doctor. She told the Doctor that Lara Zanis had breached the shields around Earth. She later informed him that the War Ollistra had been kidnapped. (AUDIO: The Shadow Vortex)
Her grandfather was a friend of Seratrix and opposed the Last Great Time War. He was killed in one of the first acts in the war. (AUDIO: Eye of Harmony)
Heleyna had accompanied Ollistra to a retreat in order to get information about a Dalek spy in the High Council. She accompanied the Doctor to Rovidia. When the Daleks spotted their ship, she used her time on the front to trick the Dalek scanners into thinking the ship they were on was a Dalek ship. On Rovidia, she was taken prisoner as Fesk recognised her as Ollistra's guard. (AUDIO: The Eternity Cage)
She was the Dalek spy and tried to kill the Doctor. Heleyna used the code name "Agent Prydon," a reference to the Prydonian Chapter to which she belonged. She betrayed her people because of what the Time Lords did to her family. Using her codes she gained as Ollistra's guard she gained access to the Eye of Harmony chamber in Vassarian's Battle TARDIS on behalf of the Dalek Time Strategist. She also sabotaged the architectural reconfiguration system to stop the Doctor from following them.
When she heard the Dalek Time Strategist's true plan to wipe out the Time Lord, she felt betrayed. She was determined to stay in the collapsing star chamber but Kalan tried to stop her. Due to her stubbornness, however, she stayed behind. The Doctor appealed to her good nature and got her to detonate a Dalek Dark Matter bomb to give Vassarian's TARDIS the energy it needed to materialise into real time. (AUDIO: Eye of Harmony)